参数

The level parameter specifies the protocol
level at which the option resides. For example, to retrieve options at
the socket level, a level parameter of
SOL_SOCKET would be used. Other levels, such as
TCP, can be used by specifying the protocol number of that level.
Protocol numbers can be found by using the
getprotobyname() function.

Tim's example might seem at first a bit non-intuitive since he is using the SO_SNDTIMEO constant. Which means, if the socket has to send out data, it must do it within the limit specified - in his case 10 seconds. Usually you won't set a timeout for sending out data. Nevertheless, the example is valid, and there are situations where you need to do so.

A more intuitive use of socket_set_option would be to set a time out for a blocking socket (a socket that waits for data to be receive when read from). You would do this like so:

Lingering will sometimes not work when you're working with non-blocking sockets. Even if the socket is set to linger and you keep tying to close until the socket doesn't return an error and the resource is no longer identifiable as type 'Socket', the socket may STILL close without sending everything.

Therefore, in the event that you are using non-blocking sockets (which is preferable if you care at all about signaling), you should set the socket as blocking (socket_set_block()) before calling to close it. This will allow everything to flush before it returns.

I would like to comment on the previous note regarding blocking sockets.There is more to blocking sockets than waiting for data to be received when trying to be read upon, just to make example, a listening blocking socket will wait for a client to try to connect before it returns when you socket_accept() it.